The older lots of SB193 I owned had a 55gr FMJ. All research led it to be a 55gr Sierra Match King FMJ. Being subsonic, it has the weird ability to penetrate soft kelvar and thinner IIIA PE plates. Some had noticed in newer FN catalogs that they tout the weight as being 62gr. This newer lot I have seems to agree with the heavier bullet weight (allowing for variance), and it seems to help with cycling the action of the FSN (probably due to velocity bump) with/without a can, and still retains the ability to keep it's shape while piling through soft kevlar. 

Amazing how effective these subsonic loads are.

Any idea of what the projectile is? SS109 would make the most sense, as thats a projectile developed by FN, but I thought they were too long to stabilize?

It's shorter than SS109.. It's entire core is lead, so I'm not sure what the projectile is. Jacket is bi metal (attracts magnet)

That is weird - and even more impressive that lead core FMJ subsonic is IIIA defeating.

Also, really makes me suspect that wax or plastic filled SS198's would be much more effective. By filling the hollow nose, it should add enough rigidity to keep the nose from smushing flat. Then they should zip right through given their velocity. Perhaps an interesting test?

Do you know, will SS109 work for subsonics?

That's something people have been trying to figure out on SS198. If it weren't for the OTM, it wouldn't mushroom over as easily.

I have not tried SS109 for subsonic, but I have M855A1, and they're too long to stabilize in 1:9. I would suspect SS109 would be too from some research I've done

The lead core was pretty darn soft.. I sectioned it with a dremel, not the best job in the world. Maybe wolfgang would section one for me..

IMG_5642 by Matt H, on Flickr

Yes, very slight line across bottom towards base.